powershell export-csv overwrite data?

this program is first create csv file and output date to csv file, and then for loop the data to csv file 

$strFileName="c:\temp\test\EMS_tag_rpt01.csv"

If (Test-Path $strFileName)

{

  # // File exists

  $rows = import-csv "c:\temp\test\EMS_tag_rpt01.csv"

  $employees = @()

#Add newly created object to the array

#$employees += $employee

for ($i=1;$i -le 2;$i++)

{    

$employee = New-Object System.Object

$employee | Add-Member -MemberType NoteProperty -Name "Creation Time" -Value $(Get-date)

$employee | Add-Member -MemberType NoteProperty -Name "Employee ID" -Value $($i.ToString("D2"))

$employees += $employee

Start-Sleep -Seconds 1

}

#Finally, use Export-Csv to export the data to a csv file

#$employees | Export-Csv -NoTypeInformation -Path "c:\temp\test\EmployeeList.csv"

$rows+$employees | Export-Csv  -Path "c:\temp\test\EMS_tag_rpt01.csv" -NoTypeInformatio

}Else{

#Export-Csv  -Path "c:\temp\test\EMS_tag_rpt01.csv"-NoTypeInformatio

#$rows = import-csv "c:\temp\test\EMS_tag_rpt01.csv"

#echo $rows

$employees = @()

#Add newly created object to the array

#$employees += $employee

for ($i=1;$i -le 2;$i++)

{

$employee = New-Object System.Object

$employee | Add-Member -MemberType NoteProperty -Name "Creation Time" -Value $(Get-date)

$employee | Add-Member -MemberType NoteProperty -Name "Employee ID" -Value $($i.ToString("D2"))

$employees += $employee 

Start-Sleep -Seconds 1

    $employees | Export-Csv  -Path "c:\temp\test\EMS_tag_rpt01.csv" -NoTypeInformatio

    $csv=Get-Content "C:\temp\test\EMS_tag_rpt01.csv"

"XXX Report,Date: $(Get-Date)" | out-File -FilePath "c:\temp\test\EMS_tag_rpt01.csv" -Encoding utf8

$csv | Out-File -FilePath "c:\temp\test\EMS_tag_rpt01.csv" -Encoding utf8 -Append

}

}